1. Field of the Invention
The present invention relates to a manufacturing method of module components, and more particularly relates to a manufacturing method of electronic module components including a self-shielding structure.
2. Description of Related Art
Various electronic module components are mounted on a smartphone and a tablet terminal that are recently in widespread use. These module components include, as basic constituent elements, a substrate with various wiring lines formed on a surface or inside thereof and a connection pad and a terminal formed on a bottom surface thereof, a passive device (an inductor, a capacitor, or the like) and a semiconductor device respectively mounted on the surface of the substrate, and a mold that covers the passive device and the semiconductor device. Among these, there is a module component further including a so-called self-shielding structure in which respective surfaces other than a terminal surface are covered with a conductive paste, and a ground potential is supplied to the conductive paste thereby enabling shielding from electromagnetic noise. Examples of such module components are disclosed in Japanese Patent Application Laid-open Nos. 2004-172176, 2004-095607, 2004-103998, 2004-207352, 2004-193187, and 2005-079139, and Japanese Patent No. 4530110.
Supply of the ground potential to the conductive paste is realized by exposing a ground wiring line, which is one of the various wiring lines formed on the substrate, on a side surface of the module component. By this method, electrical continuity is established between the conductive paste formed on the side surface of the module component and the ground wiring line exposed on the side surface, thereby enabling to supply the ground potential to the conductive paste.
The self-shielding structure can be formed by various methods as disclosed in the above seven patent documents. However, a method of applying a conductive paste by spraying as disclosed in Patent Application Laid-open No. 2005-079139 is currently considered to be most preferable. According to this method, a conductive paste with fewer bubbles as compared to other methods can be obtained.
When a conductive paste is formed by spray application in a mass production process of module components, a groove is formed by dicing between a plurality of module components formed on one panel or sheet (hereinafter, “aggregate substrate”), and a conductive paste is sprayed toward inside of the groove.
According to the conventional manufacturing method, spraying of the conductive paste as described above is performed by spraying the conductive paste directly downward from a spray nozzle provided immediately above the groove. According to this method, when the groove is shallow, the conductive paste can be formed preferably over the entire internal side surface of the groove. Therefore, the conductive paste can be formed preferably over the entire upper surface and side surface of the module component.
However, when the groove is deep, even when the conductive paste is sprayed as described above, the conductive paste may adhere only to an upper part of the internal side surface of the groove, and may not reach the lower part thereof. In this case, formation of the conductive paste becomes insufficient on the side surface of the module component, particularly in the lower part thereof (a part close to a terminal surface). According to the degree thereof, an electromagnetic shielding function may be deteriorated and electrical continuity between the ground wiring lines formed in the substrate and the conductive paste say be lost.